I'm sending a Canon FTbn to Ken Oikawa for a CLA and anything else that it may need. I was curious if there was a general consensus on whether or not to get the voltage conversion. I do happen to own a Kanto MR-9 adapter (purchased on ebay). But I figured that the conversion may make life easier.

But then I read a few threads that stated that the meter did not perform as well after the conversion and that the adapter was the way to go.

So I'm confused. The camera is on it's way to Ken, and I do plan on asking his opinion as well. But I thought I'd reach out for thoughts here.

I use a converter. I was advised by the camera repairman that I could use a 675 hearing aid battery. If I wanted to center the battery use 20 gauge automotive wire and form a circle in the battery compartment to keep the battery from moving. (The battery is not small enough to move away from the poles. The wire will make you feel better.)

I took a reading on the 1.5v Duracell 301/386 battery that I purchased, and the voltage starts off at 1.593

Using the converter (Kanto MR-9) that I purchased, the voltage drops to 1.469

Is that because the battery is new?

No, that is because the load digital voltmeters impose on the diode is way too low - good ones have a resistance deep in the MOhm range. Put some resistor (something between 5-50kOhm will give a reasonable representation of a CdS/pointer instrument camera circuit at work) in parallel, and the voltage should drop to something reasonably close to 1.35V.

Go with the MR-9 Schottky diode adapter and the Duracell 301/386.
It is the best way by far, and that combination provides for a very long-lasting metering setup. (Long battery life as opposed to a smaller battery.)

Yes. That's the problem, you still have to make a spacer of some kind if you have the camera modified, because silver oxide batteries don't come in the larger size. There are some aluminum non diode adapters from japan on ebay that are good. 12 bucks for two I think?

Go with the MR-9 Schottky diode adapter and the Duracell 301/386.
It is the best way by far, and that combination provides for a very long-lasting metering setup. (Long battery life as opposed to a smaller battery.)

The Thai one is great. All gold plated for the best conduction.
The MR-9 is steel or chromed brass, and didn't work as reliably in my Canon 7s. I think it was a conductivity issue. When I gently pulled the battery springs on the cap up to increase their tension, it worked much better. However, it is flawless with the Thai adapter.

Whether or not you put a 1.35V or 1.5V battery in it makes little difference. It is not going to need any more than an ISO tweak w/ either to perform just fine. All of mine worked perfectly w/ either battery.

Whether or not you put a 1.35V or 1.5V battery in it makes little difference. It is not going to need any more than an ISO tweak w/ either to perform just fine. All of mine worked perfectly w/ either battery.

Dear Steve,

I've heard this from several people too. The important thing to avoid, as I understand it, is alkaline cells because of their very non-linear discharge curve. Silver or lithium are preferred, and even then, some have suggested that they can affect linearity of response even at nominal voltage. Any advice on either? From you or others?

In particular, I'm thinking of MR and MR-4 meters on a Leica and a Gossen Lunasix.

The linearity of metering inaccurance might vary by camera. There are circuits with passive components and semiconductor-based meters. My OM has the latter, no calibration possibility whatsoever, and started metering correctly when I added a 1n4148 diode (couldn't find my schottky stash). My CL has a ****load of trimmer pots, you can even adjust the linearity. CL's error was nonlinear so no ISO compensation could fix it.

If you want just a battery holder to fit the battery chamber, then nobbysparrow in Japan (that's his ebay name) sells two of them for $12. It won't convert the battery voltage at all, just holds the battery. That's what I use for cameras that have had the voltage adjusted to take 1.5V.

Even in them, I use silver oxide cells, as they have a flat discharge curve. Alkaline cells will continue to run down in voltage as they drain, so who knows what voltage they are putting out today?

Go with the MR-9 Schottky diode adapter and the Duracell 301/386.
It is the best way by far, and that combination provides for a very long-lasting metering setup. (Long battery life as opposed to a smaller battery.)

This is what I use in my old Canon (F-1n, TX) cameras, and it works great. The silver oxide 301/386 batteries have a "discharge/per life" characteristic curve similar to the mercury oxide batteries that these cameras were designed for. Unlike alkaline batteries.

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